1. The Field of the Invention
The present invention relates generally to micropipette tips used in electrophoresis processes such as DNA sequencing. More particularly, it concerns a plurality of interconnected tips each having thin flattened extremities for simultaneously dispensing a plurality of biological samples between electrophoresis plates.
2. The Background Art
Proteins play a crucial role in nearly all biological processes, including catalysis, transport, coordinated motion, excitability, and the control of growth and differentiation. By studying and analyzing proteins, scientists have been able to provide important practical knowledge useable in a vast array of applications, from biomedical techniques to criminology, and many others.
The prior art methods and apparatus for studying proteins fall generally under three categories of approach, namely, electrophoresis, ultracentrifugation, and chromatography. One of the major goals in protein study is to determine how amino acid sequences specify the conformations of proteins. In electrophoresis, this is accomplished by separating and displaying the molecules of proteins and other macromolecules, such as DNA and RNA, by their molecular weight. A molecule having a net charge will move in an electric field, hence the term electrophoresis. Protein samples are dispensed in a holding matrix, an electric field is applied, and the charge-carrying molecules separate according to their weight. Once the molecules of a protein are separated and displayed in accordance with their molecular weight, the display can be studied to determine the protein's amino acid sequence.
The structural means for accomplishing "vertical electrophoresis" typically includes two opposing, vertically-disposed transparent plates disposed in a parallel, closely spaced-apart orientation for holding porous sequencing gel therebetween, such as polyacrylamide gel. Protein samples are dispensed into the gel, which is capable of suppressing convective currents produced by small temperature gradients (a requirement for effective separation), and the gel also operates as a "molecular sieve" that enhances the separation of molecules by their molecular weight. Molecules that are small compared with the pores in the gel readily move through the gel, while molecules larger than the gel pores are rendered essentially immobile. Intermediate-size molecules move through the gel with various degrees of facility. However, the molecular weights of the molecules is the principle factor that determines the separation among charge-carrying molecules, under the force of the electric field.
One of the challenges in properly conducting electrophoretic analysis is the difficulty of dispensing the protein samples into the gel with reproducible quantitative accuracy. The sample plates are spaced extremely closely together, for example by 0.20 millimeters. A lab technician must extract samples of the protein with a single channel pipettor or syringe and dispense them into individual wells formed in the sequencing gel, repeatably aspirating and dispensing each sample one at a time in the same micro-volume quantity. This requires a highly skilled technician and a large amount of time with little room for error, especially when the study involves a valuable biological sample in short supply. Accordingly, there is a need for a method and device capable of placing multiple biological samples between the electrophoresis plates more quickly and more accurately.